1. Field of the Invention
This invention relates to a method of recording pieces of image information of different kinds in corresponding classifications on a photosensitive medium in the form of rollfilm by electrophotography. The term, "image information" hereinafter used is intended to mean letters, figures, photographs and other patterns which can be recorded and reproduced (or which can be displayed by projection on a screen).
2. Description of the Prior Art
As a medium for storing such pieces of image information microfilms have come into widespread use. For the purpose of recording a large volume of image information use is made of silver halide photosensitive material or diazophotosensitive material in the form of rollfilm, microfiche or punched cards. Or account of their relatively large storage capability inspite of their small size, rollfilms and microfiches have gained general popularity and have come into wide use. Sixty or more frames (or pieces) of image information can be stored on a single microfiche sheet. The microfiche is advantageous for storing pieces of image information of different kinds in corresponding classifications. This is not the case with rollfilm. Also, the microfiche is advantageous for retrieval different kinds of image information.
Advantageously a large amount of image information can be stored if a rollfilm is used. It is, however, impossible to take full advantage of such rollfilm unless it is necessary to record a large amount of image information, i.e. enough to fill the full length of the rollfilm. In making a record on a rollfilm, pieces of image information are recorded as they occur (or in the order of their appearence) irrespective of the kind of image information. Thus the series of pieces of image information on the full length of the rollfilm are in random order as regards classification. Therefore, the retrieval of a desired kind of image information is time and labor consuming. Thus, there has been a demand for classifying and recording pieces of image information according to their kinds.
With a view to meeting this demand there has been proposed a record producing method as follows: a rollfilm having pieces of image information recorded thereon is extended and cut as long as the width of a flat jacket; and the resultant film strips are sequentially put in the flat jacket in rows, thus constituting a flat sheet similar to a microfiche. In the proposed method the number of frames exposed at one time in recording is twelve, and their equivalent length is equal to the width of a jacket, much less than the number of frames exposed at one time in making a record on a 60 frame microfiche. Of course, when recording less than twelve pieces of image information, the remaining blank frames on a single strip of film will not be used, and be wasted. The number of wasted frames will be small, compared with the other kinds of microfilm recording.
Like the ordinary microfiche, the "jacketed" microfiche stores only a fraction of the image information which can be stored in a single rollfilm, and therefore a large number of microfiches will have to be used to store as much image information as a single rollfilm can store, and the difficulty in maintenance and the storage space required will increase accordingly.
Thus, there has been an ever increasing demand for a recording medium which is capable of storing as much image information as a rollfilm which still allowing the recording of a fraction of the total frames at one time, and permitting classification of pieces of image information in terms of their kinds in recording.
This demand is hardly satisfied by the microfilms made of silver halide photosensitive material, which cannot be partially and selectively used for recording without impairing the remaining blank frames of the rollfilm or microfiche. Specifically, in some instances the remaining blank frames are undesirably exposed to light, and are thus spoiled. Otherwise, the remaining length which has not been exposed to light, will be spoiled during development of the length used. At the time of projecting and displaying selected frames bearing image information on a screen it is next to impossible to keep the remaining unused frames from being exposed to light, preventing the unused part from exposure to the light of projection. It is also difficult to shut out light from the unused part of a microfilm or microfiche when they are changed for the purpose of recording or while storing such partly used microfilms or microfiches. When a desired piece of image information in a partly used microfilm is selected and read with a projector, it will be necessary to locate the desired frame on the microfilm with the aid of non-optical means beforehand because otherwise, the retrieval operation will cause the exposure of the unused part of the microfilm to the light of projection, thus spoiling it. The reliance on non-optical means will not permit the retrieval of a desired frame in the microfilm with the eyes. Obviously, such non-optical retrieval system would be useless in practical applications. Also, it is necessary to provide fail-safe means to prevent inadvertent overstepping across the used-and-unused boundary into unused part of a microfilm when reading with a projector because otherwise, the unused part will be exposed to the light of projection, and be spoiled. There are presumably a variety of fail-safe means, but these require extra tedious work at the time of recording, and are commercially useless.
The present inventor found that all the defects mentioned above can be overcome simply by using electrophotography. Specifically, whether exposed to light or not, electrophotographic photosensitive material can be reused. Even a material which has been developed can if it has not been fixed be subjected to cleaning, and then reused. Thus, it is unnecessary to shut off light in using a selected part of a electrophotographic photosensitive microfilm. As long a part of electrophotographic photosensitive microfilm as required can be used even if the amount of image information to be recorded at one time is less than that which is enough to fill the full length of extended rollfilm, and the partly used rollfilm can be read with an optical means, while still keeping the unused part in condition for later use.